1. Field of the Invention
This invention relates to a fluorescent lamp device having an incandescent lamp base.
2. Description of the Prior Art
A fluorescent lamp is widely used for its lighting efficiency in comparison with an incandescent lamp. So it is advantageous to use a fluorescent lamp instead of an incandescent lamp from the standpoint of saving electric power during times of severe energy crisis.
However, a fluorescent lamp is generally straight or annularly shaped and further generally has its own shaped base structure at the ends thereof. Additionally, it is generally necessary to include a glow starter and a ballast to light a fluorescent lamp.
Consequently, fluorescent lamps cannot be directly coupled to an incandescent lamp base because of the above reasons.
There have been a few proposed fluorescent lamp devices having an incandescent lamp base, for example as shown in U.S. Pat. No. 3,953,761. But in such a lamp device, a large ballast is disposed in the center of the device, such that it is impossible to dispose a conventional ballast in an incandescent lamp base. However, if a ballast is constructed small and light, it would be possible to dispose such ballast in an incandescent lamp base.
Such a ballast, which uses a positive temperature coefficient characteristic thermistor, is known from Japanese Utility Model No. 1,018,720. However, this thermistor ballast has a tendency to increase its resistance value as its temperature rises. As a result, as such a termistor is heated to a predetermined temperature, its resistance value rapidly becomes large.
In such a case, the fluorescent lamp soon stops lighting since it is not possible to supply the lamp filaments with enough current to maintain an electric discharge.
Therefore it has been impossible to use such a thermistor ballast for application to a fluorescent lamp device of the above-noted type.